Process for treating polynosic fibers and products obtained thereby



p 7, 1964 R. s. KENYON ETAL PROCESS FOR TREATING POLYNOSIC FIBERS AND PRODUCTS OBTAINED THEREBY Filed Nov. 18. 1960 United States Patent 3,128,147 PROESS FDR TREATTNG PULYNGSHQ FiEERS AND PRODUQTS (BBTAINEH) TEEREBY Robert S. Kenyon and Wiiiiam Frank Taylor, Mobile, Ala, assignors, by mesne assignments, to tiourtaulds, Limited, London, Engiand, a British company Filed Nov. 18, 1960, Ser. No. 70,247 8 Claims. (Cl. 8-116) This invention relates to new textile products, particularly to regenerated cellulose products having improved dimensional stability and to methods for making such products.

The production of so-called wash and wear garments has become increasingly important in the textile industry. Such garments are intended to be wearable immediately after washing and drying; no ironing being necessary. Creases and pleats which were intentionally in the garment are retained during washing and drying; and undesirable, random creasing does not develop.

To make wash-wear goods from regenerated cellulose fibers it is necessary to cross-link the fibers, i.e., to modify the fiber chemically so that the cellulose chains are linked together at points along their lengths. Various crosslinking agents are known and have been used. These range from simple materials such as formaldehyde through the so-called reactant type resins such as dimethylol ethylene urea to complex heat hardenable resins such as the aminoplasts.

In recent years much attention has been given to a highly crystalline type of regenerated cellulose fiber. By way of explanation, it may be stated that all cellulose fibers, natural and regenerated, have amorphous and crystalline regions.

The degree of crystallinity of cellulose fibers can be measured in various ways and the values obtained vary to some extent with the manner of measurement. The values referred to above and throughout the present specification and claims are based on the X-ray method described by P. H. Hermans and A. Weidinger in Journal of Polymer Science, vol. IV, pp. 135144, 1949.

Regenerated cellulose fiber having a degree of crystallinity of 5063% can be made by spinning viscose having relatively high degree of xanthation :60 to 80) into a zinc-free low acid bath. Many processes of this type have been developed in recent years. One is described in United States Patent to Tachikawa 2,732,279. In the Tachikawa process, unaged viscose is spun into a zinc-free bath containing less than 30 g./l. H 50, and less than 50 g./l. Glaubers salt at a temperature below about 30 C. and the fibers are then drawn, in the bath, at a progressively increasing speed until regeneration is complete.

Regenerated cellulose fiber made from this and similar processes is also characterized in having a fine and stable rnicrofibrillar structure. It will also usually have a minimum wet strength of 2.2 g./denier and a wet elongation of less than 3.5% at a stress of 0.5 g./ denier. Such fibers have been referred to as Polynosie fibers.

In our copending application Serial No. 38,282, filed June 23, 1960, we have disclosed that when fabric made from highly crystalline regenerated cellulose identified above is treated with a swelling agent such as caustic soda, the tendency of such fabric to ravel is greatly reduced.

It has now been discovered that if this highly crystalline regenerated cellulose textile material having a fine and stable rnicrofibrillar structure, a minimum wet strength of 2.2 grams per denier and a wet elongation of less than 3.5% at a stress of 0.5 gram per denier is treated with a swelling agent and is afterward treated with a cross-linking agent, much better wash-wear prop- 3,128,147 Patented Apr. 7., 1964 ice erties are obtained than when the material is cross-linked without having previously been treated with a swelling agent.

The invention, therefore, comprises a method for making textile materials having improved properties which comprises treating regenerated cellulose filamentary material having a degree of crystallinity of above about 50%, a fine and stable rnicrofibrillar structure, a minimum wet strength of 2.2 grams per denier and a wet elongation of less than 3.5% at a stress of 0.5 gram per denier with a swelling agent for the cellulose, and crosslinking the cellulose so treated.

The invention further includes textile material comprising cross-linked regenerated cellulose fiber having a degree of crystallinity above about 50%, a fine and stable rnicrofibrillar structure, a minimum wet strength of 2.2 grams per denier and a wet elongation of less than 3.5% at a stress of 0.5 gram per denier, and which, prior to cross-linking, had been subjected to the action of a swelling agent, and dried.

The present process may be applied to the highly crystalline above identified material in any form, for example, in the form of staple fiber, tow, continuous filament or yarn. Preferably, however, the material is treated as fabric, woven, knitted or non-woven. (By non-woven fabric, is meant fabric in which a mass of interlocked fibers forms a blanket or bat having a substantial cohesive strength.) Fabric may be treated as a running length or in some more complex structure, e.g., as a garment.

The invention may, moreover, be applied to blends of the highly crystalline regenerated cellulose fiber identified above with other fibers, and to fabrics in which yarns of the said fiber are used concurrently with yarns of other fibers. These other fibers should preferably not be adversely affected by caustic or other swelling agents. Examples of suitable fibers include cotton, nylon, polyester (e.g., polyethylene terephthalate) acrylic, polyethylene and polyproylene fibers. The greatest advantages of the invention are obtained when the proportion of highly crystalline regenerated cellulose fiber is at least 50% by weight.

Normal regenerated cellulose fiber can be blended with the special regenerated cellulose material identified above, but when the proportion exceeds about 15% by weight, the product becomes objectionably boardy upon treatment with a swelling agent.

The invention may be practiced using an aqueous solution of virtually any conventional cellulose swelling agent. Sodium hydroxide is preferred, but other alkali metal hydroxides, e.g., potassium hydroxide, may be used, as well as such materials as zinc chloride and sodium zincate.

The concentration of swelling agent used will vary with the particular agent, with the temperature and time of treatment and to some extent with the construction of the fabric. In general, the concentration may vary between about 5% by weight and about by weight. When alkali metal hydroxides are used the concentration will normally be between 5% and say 40 With sodium hydroxide, concentrations of 5% to say 20% are preferred.

The time of treatment will vary with concentration, time, and fabric construction. In general it will range from say 15 to 50 seconds.

Treating temperature will vary with the other treating conditions but will in general be between about 15 and about 40 C.

The cross-linking step used in the present invention may be any of those conventionally employed in the art. As noted above the agent may be formaldehyde and in this case the technique disclosed in the copending application of G. C. Daul et al., Serial No. 792,696, filed February 12, 1959, now abandoned, and its continuationin-part Serial No. 81,958, filed January 11, 1961 is preferably used. Alternatively the cross-linking agent may be a reactant type resin, such for example as methylated methylol urea, N-substituted methylol triazones, methylol N-substituted triazines, methylated and unmethylated methylol ethylene ureas and methylated and unmethylated methylol 1,2-propylene ureas. Again the cross-linking agent may be an aminoplast, i.e., a heat hardenable condensation product of a compound having at least two amino hydrogens with a methylol forming compound. Typical aminoplasts are urea-formaldehyde, melamineforrnaldehyde, dicyandiamide-formaldehyde, guanidineformaldehyde and combinations of these ingredients. The term is also used to include the methylolsamino-epihalohydrin compounds described in Patent No. 2,960,484 to George C. Daul.

Other resinous materials which are suitable for use in the present invention are those formed by the reaction of formaldehyde and acrolein as described in United States Patent No. 2,696,477, resins formed by the reaction of acetone and formaldehyde 23S described, for example, in United States Patents No. 2,504,835 and No. 2,711,971; and polyepoxy resins, e.g., polyfunctional compounds having at least two epoxy groups linked through a hydrocarbon, a polyhydric phenol or a polyhydric alcohol group, such as the resins formed from saturated polyglycidyl ethers of polyhydric alcohols as described in United States Patent No. 2,752,269. Particularly useful compounds of the last named class are the condensation products of epichlorohydrin with ethylene glycols. It will be understood that the precise resin used is not a part of the present invention and other heat hardenable resins used in the textile industry may be employed as desired.

The manipulative technique used in carrying out the invention will vary and will depend largely on the physical form of the fibrous material, When the material is in the form of staple fiber, it may be treated as a blanket with both the swelling agent and the cross-linking agent applied as sprays. Tow may be passed through baths of each agent as a running strand or laid down in a platted pattern and sprayed. Continuous filament and yarn may be passed through baths or wrapped 011 rollers over which the solutions are passed. Fabric may be padded or sprayed. Garments may be dipped in the solution. Newly spun fiber is preferably treated according to the technique disclosed in Daul et al. Patent No. 2,902,391.

The cross-linking agent is normally applied as an aqueous solution or dispersion containing from say 4 to 25% agent and from l to 50% catalyst on the weight of agent. After impregnation, the textile material is normally squeezed to the desired pick-up. It may then be dried by heating, care being taken to keep the drying temperature below about 100 C. Drying time is normally 20 seconds to 2 hours. Following this the fiber, yarn or fabric may be stored for whatever period is desired. If the material was treated in raw fiber, it may be converted to yarn or fabric and stored in either of those forms. The cross-linking solution may contain various textile finishing agents, such as hand builders, lubricants, water repellents and the like as well as the cross-linking agent. In general, these other agents function in a conventional manner, i.e., their function is the same as it would be if no cross-linking agent were present.

Between the swelling treatment and the cross-linking treatment, the material may be dried and processed in various ways, e.g., made up into yarn, fabric or garments. On the other hand, it need not be dried between the two treatments. Normally, however, it will be washed between the swelling treatment and the cross-linking treatment.

The drawing is a flow diagram of a process according to the invention when the fiber treated is in fabric form.

Referring to the drawing, the fabric 1 is fed over a roller 2 into a bath 3 containing from 5 to by weight of a cellulose swelling agent. It moves through the bath over rollers and is thereby impregnated with the bath liquor. After removal from the bath, the fabric travels over rollers 5, d, 7 and 8 to a stenter frame 9. In accordance with the normal operation of a stenter frame the edges of the fabric are grasped by a series of moving clips (not shown) and stretched in the direction of the filling, transverse to the direction of fabric movement. The fabric is sprayed with water from spray heads 10 and 11, which serve to remove most of the caustic. It then moves under roll 12, over roll 13 and down into water bath 14. It passes through the bath M: under rolls 15 where any remaining swelling agent is removed. From the bath 14, the fabric moves over roll 16 and thence down into bath 17. Bath 17 is a sour bath, containing a weak acid, e.g., from 0.5% to 1.5% acetic acid. The fabric moves through the bath 1'7 under rolls 18, and is then taken out, passed over rolls 19 and delivered to water bath 20. In bath 20 the fabric is rinsed to remove acid, passing under rolls 2 1. It is taken out over rolls 22 and squeezed between squeeze rolls 23 to remove excess water. it is then passed over roller 24 and into bath 25 which is a solution of the cross-linking agent. in passing through bath 25 the fabric moves under rolls 26. It is removed from the bath, and passes over roller 27. Excess solution is removed by squeeze rolls 23 and the fabric is then taken through an oven 29 where it is dried and, if desired, also cured.

It will be understood that if desired, a drying stage may be inserted between the squeeze rollers 23 and the bath 2'5 and in fact the fabric may be removed from rollers 23, dried and shipped to some other location for crosslinking. Moreover, other processing such for example as Sanforizing may be applied between the swelling treatment and the cross-linking treatment.

The invention will be further described by means of the following specific example, which is given for purposes of illustration only, and is not to be taken as in any way limiting the invention beyond the scope of the appended claims.

Example Regenerated cellulose staple fiber having a crystallinity of 5363% was made by extruding a viscose containing 5% cellulose, 3% NaOH and having a 1 number of about 70 into a spinning bath at 28 C. containing about 3% H 80 about 5% Na SO and no ZnSO and stretching by about 100% while the filaments were still less than 50% regenerated. The resultant staple fiber 1 /2 denier x 1 7 was made into a challis fabric, warp and filling 22/1, greige width 39%".

Two batches of the fabric, after desizing, washing and drying were subjected to caustic treatment in accordance with the invention. Batch A was treated with a solution containing 6% by weight NaOH at F. Batch B was treated with 18% NaOH at 102 F. Total time of exposure to caustic was 25 seconds, in each case.

After drying, portions of each batch of fabric were impregnated with baths containing varying amounts of dimethylol ethylene urea. The make-up of these baths was as follows:

Only one sample of the fabric treated with 6% caustic was treated with resin. The samples were air dried, cured at 310 F. for 8 minutes, washed at 140 F. and dried. A nitrogen determination showed that the 18% caustic samples had absorbed 2.3%, 4.6% and 5.1% by weight DMEU from baths A, B, and C, respectively, and the 6% caustic treated sample 4.5% from bath B. Control samples of the same fabric which had not been treated with caustic, absorbed 2.6%, 4.6% and 5.3% DMEU from baths A, B, and C, respectively.

After impregnation, curing and drying the samples were tested for wash+wear rating using the technique described in the 1960 Technical Manual, AATCC, Tentative Test Method 88-1960. The results are tabulated below:

An inspection of these results shows that for equal resin applications, material which had been previously treated with caustic shows greatly improved wash-wear properties compared with material which had not been so treated.

We claim:

1. A method for making improved textile material which comprises treating regenerated cellulose textile material having a degree of crystallinity above about 50%, a fine and stable microfibrillar structure, a minimum wet strength of 2.2 grams per denier and a wet elongation of less than 3.5% at a stress of 0.5 gram per denier, with a swelling agent for cellulose equivalent to a solution containing between about and about 40% of an alkali metal hydroxide, drying the material, and subsequently impregnating said material with a cross-linking agent for the cellulose and curing the impregnated material.

2. The method claimed in claim -1 wherein the crosslinking agent is a reactant-type resin.

3. The method claimed in claim 1 wherein the swelling agent is an aqueous solution containing between about 5 and about 40% NaOH.

4. The method claimed in claim 1 wherein the crosslinking agent is dimethylol ethylene urea.

5. A textile material comprising cross-linked regenerated cellulose fiber having a \degree of crystallinity of at least a fine and stable microfibrillar structure, a minimum wet strength of 2.2 grams per denier and a wet elongation of less than 3 .5% at a stress of 0.5 gram per denier, which fiber prior to cross-linking has been subjected to the action of an aqueous solution of a swelling agent for cellulose, equivalent to a solution containing between about 5 and about 40% of an alkali metal hydroxide, and dried.

6. The material claimed in claim 5 wherein the fiber is cross-linked by means of a reactant type resin.

7. The material claimed in claim 5 wherein the aqueous solution contains between about 5 and about 20% by weight caustic soda.

8. The material claimed in claim 5 wherein the fiber is cross-linked by means of :dimethylol ethylene urea.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Walter et a1.: Textile Research Journal, February 1957, pp. 146-148, 8-1 163 Lit.

Reid et a1.: Textile Industries, November 1958, pp. I

1-10, 8-1163 Lit.

Hearle: Man-Made Textile, September 1960, pp. 42- 47, 8-116 Lit.

UNITED STATES PATENT OFFICE Patent No}, 3 l28 l47 April 7 I964 Robert SQ Kenyon et al.,

rtified, that error appears in It is hereby ce tion and that the said Letter ent requiring cox-rec corrected below.

the above numbered pats Patent should read as In the headlng to the drawlng lines 2 and 3 and in the heading to the printed specificatioh lines 2 and 3 title of TREATING POLYNOSIC FIBERS AND invention for PROCESS FOR PRODUCTS OBTAINED THEREBY".,, each occurren TEXTILE PROCESS AND PRODUCT Signed and sealed this 10th day (SEAL) Attest:

ERNEST W. SWIDER' Attesting Officer (2e read of November 19640 EDWARD J. BRENNER Commissioner of Patents 

1. A METHOD FOR MAKING IMPROVED TEXTILE MATERIAL WHICH COMPRISES TREATING REGENERATED CELLULOSE TEXTILE MATERIAL HAVING A DEGREE OF CRYSTALLINITY ABOVE ABOUT 50%, A FINE AND STABLE MICROFIBRILLAR STRUCTURE, A MINIMUM WET STRENGTH OF 2.2 GRAMS PER DENIER AND A WET ELONGATION OF LESS THAN 3.5% AT A STRESS OF 0.5 GRAM PER DENIER, WITH A SWELLING AGENT FOR CELLULOSE EQUIVALENT TO A SOLUTION CONTAINING BETWEEN ABOUT 5 AND ABOUT 40% OF AN ALKALI METAL HYDROXIDE, DRYING THE MATERIAL, AND SUBSEQUENTLY IMPREGNATING SAID MATERIAL WITH A CROSS-LINKING AGENT FOR THE CELLULOSE AND CURING THE IMPREGNATED MATERIAL. 